1. Field Of This Invention
This invention relates to a process for the production of 3-picoline.
2. Prior Art
Pyridine bases are important intermediate products in the chemical industry, for example, used in the production of nicotinic acid or nicotinic acid amide. Various processes are known for the production of pyridine bases.
2-methyl-5-ethylpyridine is produced industrially today in a fluid-phase process from acetaldehyde or paraldehyde and ammonia in the presence of very diverse catalysts, such as, ammonium salts. Small quantities of 2- and 4-picoline are obtained as by-products. 2- and 4-picoline are produced today in gas-phase reactions at a temperature of about 400.degree. C. from acetaldehyde and ammonia with the use of solid bed or fluid bed catalysts, based on alumimum silicate.
For the production of pyridine as well as 3-picoline, which continuously increases in importance, gas-phase reactions are used today. The formation of 2- and 4-picoline is suppressed in favor of 3-picoline by means of the addition of formaldehyde to the acetaldehyde. Such reaction also takes place in a solid bed or fluid bed, with aluminum silicate as the catalyst at a temperature of about 400.degree. C. According to such processes, yields of 3-picoline in the order of at most 40 to 44 percent are achieved. Besides, large quantities of pyridine are obtained.
It is also known that, instead of starting with saturated aldehydes, one can start out from unsaturated aldehydes, for example, acrolein or crotonaldehyde. Such reactions take place in the gaseous phase at a high temperature. The yields are essentially equally as high as or are somewhat lower than when saturated aldehydes are used as the starting material (see German OS No. 22 39 801).
It is further known to react acrolein with an ammonium salt of an organic acid, for example, acetic acid, in an acid reaction medium at a relatively low temperature (15.degree.to 150.degree. C.). The yields of 3-picoline are relatively low (see British Patent No. 1,240,928).